| Zugriffsnummer | 49445 |
| Dokumenttyp | Zeitschriftenartikel |
| Peer Review | mit Peer Review |
| Sprache | Englisch |
| Titel | Numerical modeling of air-vented parallel plate ionization chambers for ultra-high dose rate applications |
| Autor(in); Institution |
Paz-Martín, Jose; Departamento de Física de Partículas, Universidad de Santiago, Praza do Obradoiro, Santiago de Compostela, A Coruña, SPAIN
Schüller, Andreas; 6.2, Dosimetrie für Strahlentherapie und Röntgendiagnostik, PTB-Braunschweig
Bourgouin, Alexandra; 6.2, Dosimetrie für Strahlentherapie und Röntgendiagnostik, PTB-Braunschweig
González-Castaño, Diego M; Laboratorio de Radiofísica, Universidad de Santiago, Estrada de San Lourenzo, Santiago de Compostela, A Coruña, SPAIN
Gómez Fernández, Nicolás; Laboratorio de Radiofísica, Universidad de Santiago, Estrada de San Lourenzo, Santiago de Compostela, A Coruña, SPAIN
Pardo-Montero, Juan; Group of Medical Physics and Biomathematics, Instituto de Investigacion Sanitaria de Santiago (IDIS), Travesía da Choupana, Santiago de Compostela, A Coruña, SPAIN; Department of Medical Physics, Complexo Hospitalario Universitario de Santiago de Compostela, Travesía da Choupana, Santiago de Compostela, A Coruña, SPAIN
Gómez Rodríguez, Faustino; Departamento de Física de Partículas, Universidad de Santiago, Praza do Obradoiro, Santiago de Compostela, A Coruña, SPAIN; Laboratorio de Radiofísica, Universidad de Santiago, Estrada de San Lourenzo, Santiago de Compostela, SPAIN
|
| Quelle/Jahr | Physica Medica: 103 (2022), 147 - 156 |
| ISSN | 1120-1797 (print) ; 1724-191X (online) |
| DOI | |
| Verlag | Amsterdam: Elsevier |
| Freie Schlagworte | Dosimetry ; Parallel plate ionization chamber ; Ultra high dose rate ; FLASH radiotherapy ; Recombination correction factor |
| Zusammenfassung | Purpose: Air-vented ionization chambers have been the secondary standard for radiation dosimetry since the origins of radiation metrology. However, the feasibility of their use in ultra-high dose rate pulsed beams has been a matter of discussion, as large losses are caused by ion recombinations and no suitable theoretical model is available for their correction. The theories developed by Boag and his contemporaries since the 1950s, which have provided the standard ion recombination correction factor in clinical dosimetry, do not provide an accurate description when used under the limit conditions of ultra-high dose rates (UHDRs). Moreover, the high-ion recombination effects of ionization chambers under extreme dose-rate applications are an obstacle to the development of adequate dosimetry standards. Methods: In this article, the charge carrier transport equations within a parallel plate ionization chamber (PPIC) have been solved numerically with a double aim. First, this numerical model provides a more accurate tool that can be used to evaluate ion recombination correction for established PPICs in pulsed ultra-high dose rate regimes. Second, studying the chamber behavior in detail allow as to explore the limits of new chamber designs in order to improve their performance under UHDRs. The model presented here has been tested by measuring the instantaneous current of one unit of a Roos chamber (i.e., the time-resolved current during and after the irradiation pulse under UHDR conditions) and comparing these results with the absolute value of the simulated current. Results: The experimental data show consistent agreement with the results obtained using the numerical model. The experimental instantaneous current reveals effects such as the variation of the free electron fraction with the dose per pulse that are supported by the numerical model but cannot be explained in the framework of Boag’s theory. Conclusions: Numerical solutions of the charge carrier released and transport in ionization chambers are able to estimate the effects observed when PPICs are irradiated with ultra-high dose rate beams and to provide new insight into processes related to recombination losses at UHDRs. These models can be reliably extended to include regions where current analytical solutions are not valid. An agreement of better than 5 % between the experimental and simulated effective free electron fraction is found. We were able to reproduce the instantaneous current from a Roos chamber. The discrepancies observed between the experimental data and the numerical simulations can be attributed to the uncertainty about the transport parameters involved in the calculation. |
| Kostenfreier Zugang | Open Access Hybrid |
| Rechteinformation | CC BY 4.0 ; Creative Commons Attribution 4.0 License |
| Forschungsprojekt | 18HLT04: UHDpulse: Metrology for advanced radiotherapy using particle beams with ultra-high pulse dose rates |
| Förderinformationen (1) |
Förderername: European Commission (EC)
Förderer ID: 0000 0001 2242 8989 Förderer ID Typ: ISNI Förderprogramm: EMPIR 2018 Health Titel der Förderung: 18HLT04: UHDpulse: Metrology for advanced radiotherapy using particle beams with ultra-high pulse dose rates Förderungsnummer: 18HLT04 |
Zitierung
Paz-Martín, J., Schüller, A., Bourgouin, A., González-Castaño, D. M., Gómez Fernández, N., Pardo-Montero, J., & Gómez Rodríguez, F. (2022). Numerical modeling of air-vented parallel plate ionization chambers for ultra-high dose rate applications. Physica Medica, 103, 147–156. https://doi.org/10.1016/j.ejmp.2022.10.006